Site Records

SiteName: Ridge Quarry

Ridge Quarry, a small underground Bath-stone quarry at The Ridge near Corsham
in Wiltshire was taken over in 1915 for TNT and cordite storage. It was abandoned
shortly after the war but subsequently was to figure as a key progenitor of the
vast schemes undertaken at Corsham in preparation for the Second World War.

A
number of underground sites were examined during 1929 and 1930 with a view to
converting them for underground munitions storage. All the sites considered were
all found to be gravely deficient regarding either size, safety, means of access,
or proximity to nearest services.

By 23 May, 1930 a short list of five
possible sites had been drawn up: Chislehurst Caves, slate mines in the vicinity
of Blaenau Ffestiniog, Scout Quarry in Rossendale, Meadowbank salt mine in Cheshire,
and Ridge Quarry near Corsham. After careful consideration Ridge Quarry was chosen
specifically for further investigation as it offered 12 acres of storage space
half of which had been cleared and converted by the Ministry of Munitions for
explosive storage during the 1914-18 war. A quarry tramway connected the mine
with the GWR main line at Corsham station where there was siding accommodation
for twenty one trucks in a loading platform specially adapted for ammunition wagons.
Two foot gauge track existed in a good part of the workings serving raised stacking
platforms, and a steam winding engine capable of lifting six tons was still in
place at the top of the main entrance shaft.

Photo:No
1 slope shaft with the only section of narrow gauge track still in place Photo
by Nick Catford

In November 1934 War Office officials returned to Ridge Quarry and nearby Tunnel
Quarry for a more thorough inspection. The initial impression was favourable.
During subsequent discussions it was agreed that the quarries at Corsham could
accommodate filled shell and bulk explosives, the location being well situated
to supply the new filling factory under construction near Hereford. Tunnel Quarry
offered over forty-five acres of storage space, as opposed to a mere six acres
at Ridge, and had the major advantage of being connected directly to the GWR main
line by a branch entering a side tunnel at the eastern portal of Box tunnel. Outline
Treasury approval was granted for the purchase of both Ridge and Tunnel for £35,000.
Later Eastlays and Monkton Farleigh quarries were also purchased.

Conversion
of Ridge Quarry posed few problems as virtually all the clearing work had been
done by the Ministry of munitions during the first World War. The gross area of
the usable part amounted to nine and a half acres of which 3 and a half acres
consisted of support pillars, leaving six acres for storage.

Once sufficient
manpower had been mobilized, construction began simultaneously at Ridge, Eastlays
and Tunnel Quarry in July, 1936. Efforts were made to maintain an air of secrecy
about the works there, and by way of subterfuge it was let slip that the Ministry
of Food was building an emergency food dump. The need for underground storage
had become so great that it was made clear that Ridge Quarry must be ready to
receive stocks of explosives by the end of December 1936 and the quarry was brought
into commission in a very unfinished state to store ammunition and explosives
for the RAF and Ministry of Supply.

The mine had altered little since being
vacated by the Ministry of Munitions in 1922, but it still proved necessary to
remove a total of 96,000 tons of stone debris to provide sufficient storage space.
All the raised stacking areas constructed in the Great War were removed and the
floors rolled and levelled. The already comprehensive two foot gauge railway system
was extended to serve all the storage bays, and the existing steam winch at the
head of the access shaft was overhauled. Because the 1:3 gradient put a considerable
load on the winding plant a standby electric hauling engine was installed in case
of a breakdown of the primary set.

Plan
of Ridge Quarry

At the bottom of the main slope shaft
the rails served a primary reception and marshalling area. Nearby an old vertical
ventilation shaft was adapted for winding by the installation of a pair of counterbalanced
electric lifts running in wooden guides. This was a primitive affair with a poor
loading capacity, capable of handling only one third of the throughput of the
slope shaft.

Underground, the mine is crossed by a major slip-fault, with
the result that one half of the workings is about 20 feet lower than the other.
Two sloping haulageways were driven to connect the upper and lower sections; to
enable wagons to be drawn up these inclines two steam winches were installed,
adapted to operate on compressed air supplied by compressors housed on the surface.
Generally, however, loaded trucks were manoeuvred manually throughout the level
areas of the quarry.

Some months after stacking had begun a construction
programme was initiated, designed to produce a layout of storage areas more regular
than the random pattern of existing pillars. It was planned to reinforce the stone
pillars by corseting them with concrete, making them rectangular in section with
straight haulageways between. Concreting began early in 1938 on fifteen pillars
and a length of perimeter wall in the south east corner of the quarry, but this
operation was permanently suspended a few months later. The cost of the work and
the quantity of materials consumed were much greater than anticipated and were
out of proportion with the benefits obtained. The unfinished concrete reinforcing
can still be seen in varying degrees of completion in the quarry today and illustrates
the constructional techniques used in the larger and more sophisticated of the
Corsham depots.

A second slope shaft, the steeply graded West
Ridge incline, was reopened on 12 February 1942, to improve access to the lower
level of the mine and provide space for a further 1,500 tons of bombs. The underground
access tunnel linking this shaft to the new storage bays passed through an area
of treacherous roof formation that required substantial support to ensure safety.

Unlike the three other quarries that comprised the Corsham CAD, Ridge was
never reclassified as permanent storage, and no further development was done underground
after 1942. Surface buildings at Ridge were minimal. In line with War Office practice
the first buildings to be erected were twenty seven wooden huts to house military
police personnel, built in two groups on open land between the quarry shafts and
the lane to Corsham. The vertical lift shaft with its associated winding gear
and compressor house was immediately between the two groups of police huts. The
No.2 loading bay was the most substantial and is the only major building still
surviving.

Although War Office property, Ridge quarry was allocated to
the RAF in November 1936 for the storage of bombs and bulk explosives. It was
designated a sub unit of the Altrincham small-arms depot.

Photo:Winch
house at the top of No. 1 incline to the lower level Photo by Nick
Catford

Stacking and loading of bombs was carried out by
a team of thirty civilian gangers, employed by the RAOC but under direct control
of the RAF. The total capacity of Ridge Quarry was 13,000 tons, of which the RAF
at first required about 5,000 tons to store 500 lb and 250 lb General Purpose
(GP) bombs. By the outbreak of war RAF stocks at Ridge had expanded to 11,569
tons, including 4,000 tons of bulk TNT. At that time the RAOC retained a small
area to store 2,000 tons of bulk explosive for Army use.

During the early
months of the war Ridge Quarry was used as a temporary holding point for bulk
explosives and as a long term store for obsolete GP bombs returned from various
active airfields via the Pulham depot.